Drought-induced effects on nitrate reductase activity and mRNA and on the coordination of nitrogen and carbon metabolism in maize leaves
Drought-induced effects on nitrate reductase activity and mRNA and on the coordination of nitrogen and carbon metabolism in maize leaves
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DOI：
10.1104/pp.117.1.283
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发表时间：
1998-05-01
期刊：
影响因子：
7.4
通讯作者：
Becker, TW
中科院分区：
文献类型：
--
作者：
Foyer, CH;Valadier, MH;Becker, TW
玉米(Zea Mays L.)植株生长到九叶期。尽管氮素供应饱和，但最年轻的成熟叶片(茎上第七位)几乎没有N3-储备。干旱(缺营养液)植株表现出叶片酶活性、mRNA积累、光合作用以及碳水化合物和氨基酸含量的变化。叶片总水势和CO2同化速率在干旱开始后3d下降。干旱植物叶片中积累的淀粉、葡萄糖、果糖和氨基酸，而不是蔗糖(Suc)。最大可提取磷酸烯醇式丙酮酸羧基酶活性在水分亏缺期间略有增加，但该酶对苹果酸抑制剂的敏感性降低。最大可提取蔗糖磷酸合成酶活性因水分胁迫而降低，对抑制剂正磷酸盐的敏感性增加。叶片最大可提取硝酸还原酶(NR)活性与CO2同化速率呈正相关。硝酸还原酶的活化态和最大可浸提态硝酸还原酶活性在干旱条件下迅速下降。此时恢复营养液后，光合作用和硝酸还原酶活性迅速恢复。最大可提取的NR活性的降低伴随着NR转录本的减少，而Suc磷酸合成酶和磷酸烯醇式丙酮酸羧化酶的mRNAs受到的影响要小得多。在干旱条件下，N和C代谢的协调是通过调节蔗糖磷酸合成酶和NR的活性来保持的，这与光合作用的普遍速率相称。
Maize (Zea mays L.) plants were grown to the nine-leaf stage. Despite a saturating N supply, the youngest mature leaves (seventh position on the stem) contained little NO3- reserve. Droughted plants (deprived of nutrient solution) showed changes in foliar enzyme activities, mRNA accumulation, photosynthesis, and carbohydrate and amino acid contents. Total leaf water potential and CO2 assimilation rates, measured 3 h into the photoperiod, decreased 3 d after the onset of drought. Starch, glucose, fructose, and amino acids, but not sucrose (Suc), accumulated in the leaves of droughted plants. Maximal extractable phosphoenolpyruvate carboxylase activities increased slightly during water deficit, whereas; the sensitivity of this enzyme to the inhibitor malate decreased. Maximal extractable Suc phosphate synthase activities decreased as a result of water stress, and there was an increase in the sensitivity to the inhibitor orthophosphate. A correlation between maximal extractable foliar nitrate reductase (NR) activity and the rate of CO2 assimilation was observed. The NR activation state and maximal extractable NR activity declined rapidly in response to drought. Photosynthesis and NR activity recovered rapidly when nutrient solution was restored at this point. The decrease in maximal extractable NR activity was accompanied by a decrease in NR transcripts, whereas Suc phosphate synthase and phosphoenolpyruvate carboxylase mRNAs were much less affected. The coordination of N and C metabolism is retained during drought conditions via modulation of the activities of Suc phosphate synthase and NR commensurate with the prevailing rate of photosynthesis.